Radioactive lightning protector



Dec. 3, 1957 B. L. DONELLI 2,815,395

RADIOACTIVE LIGHTNING PROTECTOR Filed Feb. 26, 1953 INVENTOR BenedefioLuiqi Do'nelli ATTO United States Patent M RADIOACTIVE LIGHTNING PROTECTOR Benedetto Luigi Donelli, Milan, Italy, assignor to United States Radium Corporation, New York, N. Y., a corporation of Delaware Application February 26, 1953, Serial No. 339,115 Claims priority, application Italy March 26, 1952 16 Claims. (Cl. 174-4) This invention relates to radioactive lightning protectors of the type in which a metal rod equipped with a point intended to be connected to the ground is combined with means capable of ionizing the air over a considerable distance in the vicinity of the apparatus.

The lightning protector of the present invention introduces the advantages of simplicity and of economy of manufacture, and in addition is readily adaptable to all known requirements of application and has practically indefinite life.

More particularly, the lightning protector according to the invention is characterized in that the ionizing element consists of one or more electrically conductive radioactive areas as hereinafter described, applied to a suitable surface of one of the parts of the lightning protector located below its point, such as an upper surface of a single or multiple bell insulator directly below the point itself, and that an insulated metallic ring is provided below the insulator to serve as a potential accelerator and atmospheric exciter.

A preferred embodiment of a lightning protector according to the present invention is shown by Way of example in perspective view in the accompanying drawing.

Referring to the drawing, the central rod 1 preferably of highly conductive material, such as copper, is usually equipped with a point 2 at its upper end. The lower end of the rod, not shown, is adapted to be grounded in the usual manner. Attached to the upper end of the rod immediately below the point is an insulator 3 preferably of skirted or double-bell form. This insulator which may be of ceramic material has a center hole permitting the insulator to be dropped over the end of the rod 1. Such an insulator may be secured firmly to the rod in any desired manner, but it is convenient to form a shoulder on the rod against which the bottom of the insulator abuts and to secure it in place by means of nuts 9 screwed against it by means of suitable threads on the rod, as shown. Thus by removing the nuts, the insulator may readily be replaced, although experience has shown that the need for replacement is rare.

At a suitable point further down on the rod, a wheel like structure is disposed in a plane perpendicular to the axis of the rod. This structure comprises an outer rim or ring 4 and radial arms or spokes 6 which are secured at their outer ends in the central portions of T-shaped sleeves 5. In the center of the Wheel structure is a hub member 7 having a central bore through which the rod 1 passes and radially extending sockets 11 in which the inner ends of the spokes 6 are supported. The hub 7 may be secured to the rod 1 by any desired means. If it is to be permanently attached in one position it can be brazed to the rod, but if the distance between the plane of the ring 4 and the point 2 is to be changed or adjusted, as may be required in different locations, it may be semipermanently attached to the rod by passing screws or pins through the hub and the rod.

Since the material of the ring 4 should have good electrical conductivity, at least on its exterior surface, a solid 2,815,395 Patented Dec. 3, 1957 or hollow metal ring is preferred. it can be formed in one piece or in segments of a circle, if desired because such segments can readily be coupled together by the T-shaped sleeves 5, especially if the latter are also of similar metal. It is preferable that the hub 7 also be of metal, although it can be of insulating material. Spokes 6 should be of insulating material having high insulating properites because it is necessary that the ring 4 be maintained at the potential of the atmosphere or air with which it is in contact, and in a thunderstorm the potential of such air is likely to be high, whereas the lightning rod 1 with its point 2 is at earth potential or substantially so. It will be observed that the wheel structure hereby provided permits the length of the insulating spokes 6 to be as great as necessary in any particular installation thereby assuring adequate insulation between adjacent surfaces of greatly differing potential. The accelerating potential provided by the conductive insulated ring 4 positioned below insulator 3 and close to the point 2 has been found greatly to enhance the efficacy of the lightning protector in discharging the surrounding atmosphere, when employed in combination with the radioactive elements below described. The conducting ring 4 then produces an effect on the atmosphere which has been termed impact ionization.

In certain installations it may be desirable to employ more than one wheel structure, in which event one or more additional structures may be secured along the rod 1 in the manner represented by dash lines in the drawing. All of these wheels would usually be alike except that it is preferable in accordance with the above-mentioned rule that they be of increasingly greater diameters at successively greater distances from the point 2 of the rod in order that they produce the greatest excitation and ionizing effect over a maximum distance in the surrounding atmosphere.

The ionization of the atmosphere surrounding the lightning protector of the present invention is effected by radiations from a radioactive material suitably positioned. In the preferred embodiment, as illustrated, a band 8 of radioactive material, preferably of radioactive electrically conductive material as below described, is aflixed to the upper surface of the lower one of the two bells of insulator 3. If desired, another similar band may be secured to the upper surface of the upper bell, or the upper bell alone may carry the radioactive band. In most lightning rod installations it is preferable that this radioactive band be symmetrically disposed with respect to the rod, and comprise a continuous conductor although the radioactive portions need not necessarily be a continuous band. For example, the material may comprise segments of a circle. It has been found that the radioactive material is also effective when ai'fixed to portions 12 of the exterior surface of the metal ring 4. It may be disposed in a continuous band 12:: as represented on the lower ring 4a.

It appears that the great improvement provided by this invention is due primarily to the fact that the radioactive material itself is an electrical conductor which, being insulated from the central rod, comprises an accelerating electrode. As is well known, alpha particles are the most effective of the available radioactive particles in ionizing air molecules. However, their path is very short and the necessary molecular collisions are effective in producing ions only if the particles are moving with sufiicient velocity at the instant of impact. Therefore, by employing a radioactive accelerating electrode, according to this invention, the greatest possible initial ionization is produced, and furthermore, the ions themselves are accelerated and directed in the most effective manner to produce greatly multiplied ionization by subsequent ionic collisions. Thus 3 by a form of chain reaction there is generated an avalanche of ions which heretofore has never existed in con nection with such structures.

The provision of the metallic ring disposed at the correct distance from the grounded point of the rod and maintained at the high potential of the surrounding atmosphere, in combination with an adequate intervening or coalescent ionizing source, produces the mentioned highly conductive discharge path (apparently of conical form) extending upwardly and outwardly from the rod for a considerable distance. By experience based on a large number of installations it has been found that the resulting discharged atmospheric region is so great that lightning bolts as such do not strike structures properly protected by the lightning protectors of the present invention.

In view of the fact that lightning protectors are necessarily exposed to the deteriorating effects of atmospheric conditions it is necessary that the materials employed in the manufacture of the device be selected to withstand such effects, and without reduction of the required radioactive emission. Copper has, of course, been Widely used for lightning rods and protectors; and, in connection with the present invention, stainless steel has proved very satisfactory as the material for the ring 4 and sleeves 5. The nature of the materials of the radioactive areas or bands above referred to is of even greater importance. For this reason the invention contemplates the use of radioactive metallic foils of the nature described in U. S. Patents No. 2,326,631 to Fischer, and Nos. 2,476,644 and 2,479,882 to Wallhausen et al. Such radioactive foils can be fabricated to produce substantially any desired degree of radioactive emission, especially of alpha parti' cles, and yet are chemically and physically stable and permanent.

I claim:

1. A lightning protector comprising a central conductive rod terminating in the air at its upper end, said rod being adapted to be connected to ground at its lower end, a bell-shaped insulator attached to and surrounding the rod adjacent said upper end, the bell of said insulator having an upper surface, a band-shaped electrode of electrically conductive radioactive material affixed to said upper surface concentric to said rod, said radioactive ma terial being of the type having the property of emitting air-ionizing particles, and a wheel-like structure afiixed to said rod below said insulator in a plane perpendicular to the rod, said structure comprising a ring of conductive material and a plurality of spoke members at least in part of insulating material alfixed to said rod at their inner ends and afiixed to said ring for supporting the same at their outer ends.

2. A lightning protector according to claim 1 in which the diameter of said ring is greater than the distance between said upper end and the plane of the ring, and the external surface of the ring constitutes a substantially continuous conductor in contact with the air, whereby to form a symmetrical high-potential field in which said electrode is disposed.

3. A lightning protector according to claim 2 which includes a plurality of said Wheel-like conductive structures of increasingly greater diameters affixed along and insulated from said rod at successively greater distances from said upper end whereby to intensify and control the shape of said field.

4. A lightning protector according to claim 1 in which said radioactive material comprises an annular band of radioactive metallic foil.

5. A lightning protector according to claim 1 in which the rim of the wheel-like structure is a hollow metal tube.

6. A lightning protector comprising a central conductive rod terminating in a point at the upper end, said rod being adapted to be connected to ground at its lower end, a bell-shaped insulator attached to and surrounding the rod adjacent said point, the bell of said insulator having an upper surface, banded radioactive material affixed to said upper surface, said radioactive material being electrically conductive and of the type having the property of emitting air-ionizing alpha particles, and a wheel-like structure affixed to said rod below said insulator in a plane perpendicular to the rod, said structure comprising a circular rim of diameter considerably greater than that of said bands, at least portions of the external surface of said rim being radioactive, said rim including said radioactive portions and comprising a continuous electrically conductive band around said external surface substantially concentric to said rod and a plurality of spoke members at least in part of insulating material aifixed to said rod at their inner ends and affixed to said rim at their outer ends.

7. A lightning protector according to claim 1, in which portions of the external surface area of said ring are covered with radioactive metallic foil in electrical contact therewith so as to form a radioactive electrode insulated and spaced from said rod.

8. A lightning protector including a central conductive rod having an upper end, said rod being adaped to be connected to ground at its lower end, an insulator attached to and symmetrically surrounding said rod near its upper end, a band of radioactive material attached to the external surface of said insulator, an electrically conductive ring afiixed to said rod below said insulator in a plane perpendicular to the rod, and insulating means supporting said ring on said rod whereby said ring is adapted to assume a high-potential charge from the surrounding atmospheric electric field and a symmetrical cone-shaped electric field is thereby formed between said ring and the end of said rod above said insulator, the material of said band being of the type from which ionizing radioactive particles are emitted into the atmosphere and which has sufficient electrical conductivity to comprise an electrode adapted to assume a uniform electric particleaccelerating charge from said cone-shaped field.

9. A lightning protector according to claim 8 in which the portion of said rod between said upper end and said insulator comprises substantially the only grounded portion of the protector above said insulator.

10. A lightning protector according to claim 8 in which the portion of said rod between said upper end and said insulator comprises substantially the only grounded portion of the protector above said insulator, said ring is spaced considerably farther from said rod than is said band, and said ring includes radioactive material symmetrically disposed on its periphery, the surface of said ring thereby comprising a substantially continuous particle-accelerating electrode.

11. A lightning protector according to claim 8 in which said radioactive material is of the type which emits radioactive particles including an effective proportion of ionizing alpha particles.

12. A lightning protector including a central conductive rod having an upper end, said rod being adapted to be connected to ground at its lower end, an electrically conductive ring supported by said rod below the upper end thereof in a plane perpendicular to the rod, highpotential insulation separating said ring from said rod, and electrically conductive metallic radioactive areas on the surface of said ring such that radioactive particles are emitted therefrom, the resulting radiation-emitting member thereby comprising a substantially continuous electrode surrounding said central rod and adapted to assume a uniform electric particle-accelerating charge from a surrounding atmospheric electric field.

13. A lightning protector including a central metallic conductor rod having an upper end, said rod being adapted to be grounded at its lower end, a metal conductive ring supported by said rod below the upper end thereof in a plane perpendicular to said rod, said ring being of diameter at least as great as its distance from said upper end, high-potential insulation separating said ring from said rod, and radioactive metallic foil secured to the surface of said ring such that radioactive particles including alpha particles are emitted from said foil, said foil being in electrical contact with said ring and therewith comprising a substantially continuous electrode adapted to assume a uniform high-potential electric alpha-particle-accelerating charge from a surrounding atmospheric electric field.

14. A lightning protector including a central conductive rod having an upper end, said rod being adapted to be connected to ground at its lower end, an insulator tached to and symmetrically surrounding said rod near its upper end, a band of electrically conductive material attached to the external surface of said insulator, an electrically conductive ring affixed to said rod below said insulator in a plane perpendicular to the rod, and insulating means supporting said ring on said rod whereby said ring is adapted to assume a high-potential charge from the surrounding atmospheric electric field and a symmetrical cone-shaped electric field is thereby formed between said ring and the end of said rod above said insulator, at least a major portion of said band being of material of the type from which ionizing radioactive particles are emitted into the atmosphere and which also has suflicient electrical conductivity to cause said band to comprise a substantially continuous electrode adapted to receive from said cone-shaped field a uniform particleaccelerating electric charge.

15. A lightning protector including a central conductive rod having an upper end, said rod being adapted to be connected to ground at its lower end, an electrically conductive band-like member supported by said rod below the upper end thereof in a plane substantially perpendicular to the rod, high-potential insulation separating said member from said rod, and metallic radioactive areas symmetrically disposed on the surface of said member 6 such that radioactive particles including alpha particles are emitted therefrom, the resulting radiation-emitting member thereby comprising a substantially continuous electrode surrounding said central rod and adapted to receive from a surrounding atmospheric electric field a uniform alpha-particle-accelerating electric charge.

16. A lightning protector including a central conductive rod having an upper end, said rod being adapted to be connected to ground at its lower end, an electrically conductive band-like member supported by said rod below its upper end thereof in a plane substantially perpendicular to the rod, and high-potential insulation separating said member from said red, at least a major portion of the periphery of said member having a radioactive metallic surface such that radioactive particles are emitted therefrom, the resulting radiation-emitting member thereby comprising a substantially continuous electrode surrounding said central rod and adapted to receive from surrounding atmospheric electric field a uniform particleaccelerating electric charge.

References Cited in the file of this patent UNITED STATES PATENTS 29,933 Wooster Sept. 4-, 1860 2,025,338 Capart Dec. 24, 1935 2,326,631 Fisher Aug. 10, 1943 2,476,644 Wallhausen et al. July 19, 1949 2,644,026 Grenier et a1. June 30, 1953 FOREIGN PATENTS 429,004 Great Britain May 22, 1935 OTHER REFERENCES A. S. E. E. Definitions of Electrical Terms (1942), page 95. (Copy in Scientific Library.) 

